Aerobic exercise modulates intracortical inhibition and facilitation in a nonexercised upper limb muscle

Abstract

BackgroundDespite growing interest in the relationship between exercise and short-term neural plasticity, the effects of exercise on motor cortical (M1) excitability are not well studied. Acute, lower-limb aerobic exercise may potentially modulate M1 excitability in working muscles, but the effects on muscles not involved in the exercise are unknown. Here we examined the excitability changes in an upper limb muscle representation following a single session of lower body aerobic exercise. Investigating the response to exercise in a non-exercised muscle may help to determine the clinical usefulness of lower-body exercise interventions for upper limb neurorehabilitation.MethodsIn this study, transcranial magnetic stimulation was used to assess input–output curves, short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI) and intracortical facilitation (ICF) in the extensor carpi radialis muscle in twelve healthy individuals following a single session of moderate stationary biking. Additionally, we examined whether the presence of a common polymorphism of the brain-derived neurotrophic factor (BDNF) gene would affect the response of these measures to exercise.ResultsWe observed significant increases in ICF and decreases in SICI following exercise. No changes in LICI were detected, and no differences were observed in input–output curves following exercise, or between BDNF groups.ConclusionsThe current results demonstrate that the modulation of intracortical excitability following aerobic exercise is not limited to those muscles involved in the exercise, and that while exercise does not directly modulate the excitability of motor neurons, it may facilitate the induction of experience-dependent plasticity via a decrease in intracortical inhibition and increase in intracortical facilitation. These findings indicate that exercise may create favourable conditions for adaptive plasticity in M1 and may be an effective adjunct to traditional training or rehabilitation methods.

Physical activity levels determine exercise-induced changes in brain excitability

“…Previous study reports increase in ICF following moderate intensity exercise [15]. The disparity between previous work and our study may be attributed to differences in exercise or TMS protocols (% AMT vs. % RMT).…”

“…Previous studies report reductions in SICI following moderate intensity exercise (~20% in [16] and ~35% in [15]). In our study, we observed an overall decrease of ~18%.…”

No changes in corticospinal excitability, biochemical markers, and working memory after six weeks of high‐intensity interval training in sedentary males

“…; Singh et al. ; Lulic et al. ), there are no reports of the effects of long‐term exercise interventions on corticospinal output and intracortical circuitry.…”

“…Further, Singh et al. () have observed increased intracortical facilitation (ICF), while Lulic et al. () found decreased ICF in the M1 representations of upper limb muscles not involved in the exercise following a single biking session.…”

Movement-Based Priming: Clinical Applications and Neural Mechanisms

“…Also, M1 has shown to exhibit higher levels of activation during exercise (Christensen et al, 2000), and it is possible that this activation may help prime subsequent movements. An acute bout of lower extremity cycling exercise (20–30 min) at moderate and high intensity has been reported to reduce SICI in the M1 that lasts for up to 30 min after exercise (Singh, Duncan, Neva, & Staines, 2014; Smith, Goldsworthy, Garside, Wood, & Ridding, 2014). It is important to note that, in both these studies, the global effect of exercise was studied by examining M1 excitability of an unexercised upper limb muscle.…”